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This study was undertaken to evaluate and determine morphological characteristics which might prove valuable in the identification of the larvae of the following species of ticks of the genus Dermacentor Koch: D. albipictus Packard, D. andersoni Stiles, D. hunteri Bishop, D. parumapertus Neuman, and D. variabilis Say. A taxonomic key for the identification of all of the Canadian and United States species of the larvae of the genus Dermacentor Koch cannot be constructed until specimens of D. halli and D. occidentalis have been examined. However, the followng conclusions were reached regarding the species studied: 1. Position of setae is of no value in differentiation between the species studied. 2. The length of the scutal, sternal, premarginal, preanal, and coxal seta- are of value in the separation of the species studied. 3. The dermal sensilla was the only sensilla found to have any taxonomic value in the identification of species. 4. The determination of the degree of taxonomic significance of the leg sensillae awaits improved techniques in spreading, mounting and clearing specimens. 5. The size of the hypostome, palps, and tectum is taxonomically important in identification of species. 6. The presence or absence of coxal spurs was shown to be of questionable taxonomic significance. 7. The presence or absence of cornua is important in distinguishing between the species studied.

The literature dealing with the larva of Pacific Coast brachyuran crabs is slight. The prominent papers, those of Aikawa (1927, 1928, 1929, 1933, 1937), deal with a variety of genera and offer information useful in determin- ing family relationships. A single paper by Hart (1935) also deal with a number of brachyuran larvae found in the Pacific Ocean. None of these papers, however, identifies to species any member of the genus Cancer, although one member, C. magister (Dana) is of considerable economic importance on the pacific coast of North America. In the fall of 1958 an investigation was under taken to identify the larval stages of members of the genus Cancer. This work was accomplished under a contract with the California Department of Fish and Game, Division of Marine Resources.

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<p>Recent observations illustrate fruit fly larval attraction to the distinct odour emanating from food occupied by other larvae. Growing evidence of bacteria as influential microorganisms of hosts suggested the closer examination of host-microbial interactions. We investigated the origin of the volatiles that are attractive to flies. Focal larvae showed no difference in attraction to axenic used food with axenic larvae and axenic fresh food. Additionally, mated females showed no difference in attraction to axenic used food with axenic larvae and axenic fresh food. When we supplemented the axenic disks with <em>L. brevis</em>, larvae showed a significant preference for the axenic used food with axenic larvae and <em>L. brevis </em>over axenic fresh food. Also, the supplementation of <em>L. plantarum</em> to axenic disks also resulted in larvae showing a significant preference for the axenic used food with axenic larvae and <em>L. plantarum </em>over axenic fresh food. Focal larvae showed a significant preference for <em>L. brevis</em> on scratched MRS agar and axenic used food with axenic larvae, but did not show a significant preference for <em>L. brevis</em> on scratched axenic food. In a learning experiment, focal larvae showed no preference for novel odours previously paired with standard used food over novel odours previously paired with axenic used food. In order to test whether <em>L. brevis</em> improves food quality, the three fitness parameters observed, larval development rate, egg-to-adult survival, and adult body mass, revealed inexplicable findings. These results provide evidence for the role of bacterial volatiles in mediating the social attraction observed in fruit flies.</p> / Master of Science (MSc)